edu.uci.isr.yancees.dispatcher
Class EventDispatcher

java.lang.Object
  edu.uci.isr.yancees.dispatcher.EventDispatcher

All Implemented Interfaces:

EventDispatcherInterface

public class EventDispatcher

extends java.lang.Object

implements EventDispatcherInterface

This class works as a wrapper around an event dispatcher implementation, It allows the registratoin of different adapters for to handle the content-based subscriptions of the system.

Constructor Summary

protected

EventDispatcher() This constructor, as protected, prevents the direct instantiation of this object, and guarantees the singleton characteristic of this class.

Method Summary

void	addAdapter(EventDispatcherAdapterInterface adp) Configures the event dispatcher with the proper adapter.
void	connect() Starts the connection with the notification servers that the adapter wrapps.
void	connect(java.lang.String address) Connects and initializes the registered dispatchers This method is used by the server-specific adapters
java.util.Vector	getAdapterList()
static EventDispatcher	getInstance() The only way to access the unique instance of EventDispatcher is by using this access method
void	publish(EventInterface evnt)
void	removeAdapter(EventDispatcherAdapterInterface adp)
void	resumeDispatcher(EventDispatcherListenerInterface li) resumes the delivery of notifications to the given subscriber n.
void	shutdownDispatcher() closes this Dispatcher service access point.
void	subscribe(java.lang.String adapterName, SubscriptionInterface sub, EventDispatcherListenerInterface li) This is a specific subscriber, that sends a message to the specfific adapter installed in the system
void	subscribe(SubscriptionInterface sub, EventDispatcherListenerInterface li) subscribes for sequences of events matching pattern p.
void	suspendDispatcher(EventDispatcherListenerInterface li) suspends the delivery of notifications to the given subscriber li.
void	unsubscribe(EventDispatcherListenerInterface li) cancels all the subscriptions posted by n.
void	unsubscribe(java.lang.String adapterName, EventDispatcherListenerInterface li)
void	unsubscribe(java.lang.String adapterName, SubscriptionInterface sub, EventDispatcherListenerInterface li)
void	unsubscribe(SubscriptionInterface sub, EventDispatcherListenerInterface li) cancels the subscriptions, posted by li, whose subscripton sub' is covered by subscripiton p.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EventDispatcher

protected EventDispatcher()

This constructor, as protected, prevents the direct instantiation of this object, and guarantees the singleton characteristic of this class. The protected modifyer allows this class to be subclassed, permiting the over- load of the constructor.

Method Detail

getInstance

public static EventDispatcher getInstance()

The only way to access the unique instance of EventDispatcher is by using this access method

addAdapter

public void addAdapter(EventDispatcherAdapterInterface adp)

Configures the event dispatcher with the proper adapter. The dispatcher is a façade to the implementation-specific adapter. The use of this façade allows the runtime change of the adapter. Otherwise a simple inheritance would be enough.

removeAdapter

public void removeAdapter(EventDispatcherAdapterInterface adp)

connect

public void connect()

Starts the connection with the notification servers that the adapter wrapps.

connect

public void connect(java.lang.String address)

Description copied from interface: EventDispatcherInterface

Connects and initializes the registered dispatchers This method is used by the server-specific adapters

Specified by:

connect in interface EventDispatcherInterface

Parameters:

address - is the address of the server.

getAdapterList

public java.util.Vector getAdapterList()

Returns:

the list of adapters that is being currently used.

publish

public void publish(EventInterface evnt)
             throws DispatcherException

Specified by:

publish in interface EventDispatcherInterface

Throws:

DispatcherException

See Also:

Event

subscribe

public void subscribe(SubscriptionInterface sub,
                      EventDispatcherListenerInterface li)
               throws DispatcherException

Description copied from interface: EventDispatcherInterface

subscribes for sequences of events matching pattern p.

Notice that given the distributed nature of some implementations of Dispatcher interface, there exist race conditions that might affect the semantics of subscriptions. A subscriber might miss some notifications published before or while the subscription is processed by Dispatcher.

Also, keep in mind that the current implementation of Dispatcher does not enforce any temporal order for the delivery of notifications. This limitation might affect the recognition of patterns. For example, two notifications x and y, generated at time t_x and t_y respectively, with t_x < t_y, in that order matching a pattern P=(f_x f_y), might in fact reach the subscriber at times T_x and T_y, with T_x > T_y, in which case pattern P would not be matched.

Specified by:

subscribe in interface EventDispatcherInterface

Parameters:

li - is the subscriber

sub - is the subscription pattern

Throws:

DispatcherException

See Also:

EventDispatcherInterface.unsubscribe(edu.uci.isr.yancees.SubscriptionInterface, edu.uci.isr.yancees.dispatcher.EventDispatcherListenerInterface)

unsubscribe

public void unsubscribe(SubscriptionInterface sub,
                        EventDispatcherListenerInterface li)
                 throws DispatcherException

Description copied from interface: EventDispatcherInterface

cancels the subscriptions, posted by li, whose subscripton sub' is covered by subscripiton p.

Unsubscriptions might incurr in the same kind of race conditions as subscriptions. Dispatcher will stop sending notifications to the subscriber only after it has completed the processing of the unsubscription. Due to the distributed nature of some implementations of Dispatcher, this might result in some additional ``unsolicited'' notifications.

Specified by:

unsubscribe in interface EventDispatcherInterface

Parameters:

li - is the subscriber interface

Throws:

DispatcherException

See Also:

EventDispatcherInterface.subscribe(edu.uci.isr.yancees.SubscriptionInterface, edu.uci.isr.yancees.dispatcher.EventDispatcherListenerInterface)

unsubscribe

public void unsubscribe(EventDispatcherListenerInterface li)
                 throws DispatcherException

Description copied from interface: EventDispatcherInterface

cancels all the subscriptions posted by n.

Specified by:

unsubscribe in interface EventDispatcherInterface

Parameters:

li - is the subscriber

Throws:

DispatcherException

See Also:

EventDispatcherInterface.subscribe(edu.uci.isr.yancees.SubscriptionInterface, edu.uci.isr.yancees.dispatcher.EventDispatcherListenerInterface)

suspendDispatcher

public void suspendDispatcher(EventDispatcherListenerInterface li)
                       throws DispatcherException

Description copied from interface: EventDispatcherInterface

suspends the delivery of notifications to the given subscriber li.

Specified by:

suspendDispatcher in interface EventDispatcherInterface

Parameters:

li - subscriber to be suspended

Throws:

DispatcherException

resumeDispatcher

public void resumeDispatcher(EventDispatcherListenerInterface li)
                      throws DispatcherException

Description copied from interface: EventDispatcherInterface

resumes the delivery of notifications to the given subscriber n.

Specified by:

resumeDispatcher in interface EventDispatcherInterface

Throws:

DispatcherException

shutdownDispatcher

public void shutdownDispatcher()
                        throws DispatcherException

Description copied from interface: EventDispatcherInterface

closes this Dispatcher service access point. This method releases any system resources associated with the access point. In case this access point is connected to other Dispatcher servers, this method will properly disconnect it.

Specified by:

shutdownDispatcher in interface EventDispatcherInterface

Throws:

DispatcherException

subscribe

public void subscribe(java.lang.String adapterName,
                      SubscriptionInterface sub,
                      EventDispatcherListenerInterface li)
               throws DispatcherException

Description copied from interface: EventDispatcherInterface

This is a specific subscriber, that sends a message to the specfific adapter installed in the system

Specified by:

subscribe in interface EventDispatcherInterface

Parameters:

adapterName - is the name of the adapter to specifically subscribe to

sub - is the subscription

li - is the listener interface

Throws:

DispatcherException

unsubscribe

public void unsubscribe(java.lang.String adapterName,
                        SubscriptionInterface sub,
                        EventDispatcherListenerInterface li)
                 throws DispatcherException

Specified by:

unsubscribe in interface EventDispatcherInterface

Parameters:

adapterName -

sub -

li -

Throws:

DispatcherException

unsubscribe

public void unsubscribe(java.lang.String adapterName,
                        EventDispatcherListenerInterface li)
                 throws DispatcherException

Specified by:

unsubscribe in interface EventDispatcherInterface

Parameters:

li -

Throws:

DispatcherException